static

Learn class-level members with static.

static

A static field belongs to the class itself, not to instances. All instances share the same value. It is written with the static keyword and accessed through the class name.

Example: class Counter { static int count = 0; Counter() { count++; } }. Here count is static; each new instance increments Counter.count. Access via instance c.count also works but is not recommended; the class name is the right form. Static fields fit counters, caches and configuration values.

static methods

Methods can also be static. A static method is called on the class name without an instance; it cannot reach instance fields, only static ones.

Example: class MathHelper { static int square(int n) => n * n; }. Here square is static; it is called as MathHelper.square(5), no instance needed. Writing MathHelper h = MathHelper(); h.square(5) is not wrong but is not recommended. Static methods fit helper functions and calculations; Dart's Math.sqrt and similar functions use this shape.

Exercise Write Counter with static

Define a class named Counter. Add a static int count = 0; field. Write a Counter() { count++; } constructor. In main, create two instances with var a = Counter(); and var b = Counter();, then call print(Counter.count).

Show example solution

// Define the Counter class
class Counter {
  static int count = 0;
  Counter() {
    count++;
  }
}

void main() {
  var a = Counter();
  var b = Counter();
  print(Counter.count);
}

Test yourself

Add the static keyword

class Counter {
  ____ int count = 0;
  Counter() {
    count++;
  }
}

Show answer

class Counter {
  static int count = 0;
  Counter() {
    count++;
  }
}

When two Counter instances are created, what is Counter.count?
- 0
- 2
- 1
- Throws an error
Show answer

2 — Each constructor call increments count; two instances give 2.
Match the static parts

static

Keyword
Counter.count

Access via class
count++

Increment in constructor

Next lesson: Summary - Encapsulation

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